Blast air heating stove in metallurgical furnaces and the like



2 Sheets-Sheet 1 Anonuevs April 30, 1968 K. w. STOOKEY BLAST AIR HEATINGSTOVE IN METALLURGICAL FURNACES AND THE LIKE 'IIIIII Filed Oct. 24, 1965April 30, 1968 K. w. STOOKEY 3,380,723

BLAST AIR HEATING STOVE IN METALLURGICAL FURNACES AND THE LIKE 2Sheets-Sheet 2 Filed Oct. 24, 1965 smmflg w wwl 0 0 4 $9 0 0 fl 0 0 0 fl0 0$ v-0 0 0 0 0 0 0 0 0 0 0 \QQQQOQOOQQOOOQQQOO 0 0 0 0 0 0 0 0 0 0000000000 Q A vb'so' o INVENTOP.

KENNYIH W. Sroom 00 0 0 0 0 00 000i. 00000 0 0 0 0 0 0 0 000000000000005 0 0 0 0 0 0 0 0 0 0 0 0 0- Q 0000000000000; 0 0 000000000000 00 00000000 0 0 0000000 kQ 0 0 0 00n0 0 0 0n0 9 v\ 6 0 0 0 0W0 iiEE FIQZ

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ATTORNEVS United States Patent 3,380,723 BLAST AIR HEATING STOVE INMETALLURGICAL FURNACES AND THE LIKE Kenneth W. Stookey, Markle, Ind.46770 Filed Oct. 24, 1965, Ser. No. 504,820 8 Claims. (Cl. 26319)ABSTRACT OF THE DISCLOSURE A blast air heating stove is provided with acombustion chamber at the top of the stove which is of a conicalconfiguration and includes a slide valve which determines the degree ofmixing of the fuel and air within the combustion chamber, such mixingdetermining the rate of flame propagation and flame length. The blastair heating stove does not require preheat of air or gas for attainingthe proper flame speed, flame propagation, and so forth.

This invention relates to an improved blast air heating stove formetallurgical furnaces and the like, and to a combination of such astove with a burner and combustion chamber which is capable of moreefficiently heating air which is passed through the stove in conjunctionwith metal-producing operations.

Current metal-producing operations, and particularly steel-producingoperations, have necessitated supplies of preheated air at highertemperatures and in greater amounts. This demand for greater air blastis because of the better prepared and higher iron concentrates now beingused as furnace charge stock as compared to the previously used straightones. This improved charge can tolerate a substantially higher blastrate and so greatly increases the furnace capacity if sutficient blastair is available. In an effort to meet this demand for highertemperatures or greater volumes of heated air the art has turned toincreasing the physical size of the heat exchanger. For example, thoseskilled in the art have attempted to solve the problem by merely addingadditional height to the heat exchanger. This expedient producesdisappointingly meager results. An increase in height of the heatexchanging tower in spite of the addition of a greater mass ofrefractory bodies has not yielded proportionately greater blast rate ora proportionately increased temperature which can be used for thesteel-making operation.

It is known that the upper or top portion of the ceramic charge providesthe greatest heating effect to the air blast. Merely adding height tothe heat exchanger raises this portion of the heat exchanger withoutadding appreciably to the capacity or efficiency of the heat exchanger.What is needed, therefore, is an improved stove in which a larger volumeof air can be passed through to meet the increased demand for heated airin steel-producing operations and also, if possible, to produce anincrease in temperature as well. The need for this supply of additionalsensible heat in substantial amounts is particularly acute where theblast furnace is supplied with various hydrocarbon fuels which areinjected through the tuyeres. This is an advantageous method ofoperation because cheaper injectants permit reduction of high pricedcoke per ton of metal produced and therefore such hydrocarbon fuelinjectants are important from an economy standpoint but it is onlypossible to use these injectants where there is an adequate supply ofhigh temperature air because the materials are endothermic in theireffect on the furnaces hearth temperature.

As less coke is needed in the burden, it can be replaced with iron oreand consequently the steel making capacity of the furnace is increasedbut this also demands a further air flow. It can be now seen howimportant the air supply is.

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In a distinctly different effort to increase the efficiency of the stovesome attempts have been made to provide an external combustion chamberwhich is located exteriorly of the furnace and having ceramic or otherrefractory packing in place of the combustion chamber previously locatedinteriorly of the stove.

However, the cost of these outside combustion chambers is quite high andfrequently their installation is also confronted with space problems.Also there are maintenance difficulties inherent in them due todifferential expansion of the structure connecting the two chambers.Also, there is a tendency for some unevenness of heat distributionbecause the hot gases have a velocity head which tends to carry thegreater mass to the far side of the setting. This same connection areawill have refractory problems requiring frequent maintenance and whichwill increase in relation to the temperatures developed therein.

Other designers are offering combustion system designs that have burnersfiring from the stove sidewall at a point just over the top of thechecker setting. Extreme care must be exercised with this arrangement orsome combustion will take place down in the flues to the detriment ofthe checkers and loss of heat distribution control. To get suitabledistribution of heat, multiple burners are re quired which increase thecosts of combustion and maintenance. Such designs can also create stovedome trouble.

What the present invention proposes is to eliminate the verticalcombustion chamber Within the stove and install additional checkers inits stead. In combination with said greater utilization of internalchamber, I propose to remove the conventional hemispherical steel domeand in its place install a conical top of suflicient height and a properangle of divergence to produce an ideal burner combustion tunnel. Infact, the entire void above the checkers to the top of the refractorylined cone is made a part of a large burner. On the top of the cone isan especially designed gas/ air mixer to give a very rapid and thoroughmixing of the two materials which will produce a stable flame retentiondespite the leanness of the gas even at high input rates. Such rates ofburning are not possible in present vertical combustion chambers. Theintensity of the flame produced and the input rate would soon scour outthe skin Wall of the tunnel opposite the burner discharge. This cannotoccur in my large and diverging tunnel and consequently input rates canbe increased much beyond present ones. This will be reflected in theability to release more heat and obtain faster recoveries.

Because of the nature of the burner and its diverging combustion Zone,the heat of the fully combusted products will give an absolutely uniformdistribution as it enters the checkers. Also, due to the nature of theair/ fuel mixing mechanism of the burner the control of flame length issuch that it can be lengthened or shortened as may be desired.

It is one of the foremost objects of the present invention to provide animproved stove construction which substantially increases the capacityof existing stove structures for producing greater volumes of preheatedair which can be raised to higher temperatures. It is a further objectof the present invention to provide a novel structure and location ofcombustion chamber which enables more eflicient utilization of thecombustion volume available and of the ceramic heat-exchanging packingwithin the tower of the stove to generate a greater supply of hightemperature air but without in any way injuring the packing or reducingits useful service life.

It is a further object of the present invention to provide, incombination with a heat exchange to'wer, a new and improved combustionchamber having a simple burner, a combination mixing and combustionchamber, which is capable of producing high combustion rates and with acontrolled flame propagation so that none of the flame will impingedestru'ctively on the packing of the heat exchanger so as to necessitatepremature replacement of the packing.

As a part of this last mentioned object of the invention, there isprovided novel regulating means for controlling the rate of burning aswell as such parameters as intensity of burning and flame propagation toachieve the optimum generation of heat during the heat-up cycle of therefractory packing, which is then followed by a blast of air which isincreased in temperature by sweeping over the previously heatedrefractory packing.

An important object of the present invention is to produce a stovehaving a greater quantity of checkerwork by reason of eliminating thevertical heating chamber previously present and thereby adding heatcapacity to the stove.

An important feature of the present invention is utilizing an improvedheating chamber which provides greater uniformity of heating, highertemperatures, faster recovery and yet is operable with leaner fuels andhigher temperatures, all of this being accomplished without sacrifice ofservice life of the checkers or requiring any added maintenance.

These results are achieved not only by the novel placement of thecombustion chamber but also because of its novel configuration, that is,a novel configuration making it possible to control the variousparameters of flame propagation, heating rate and nondestructive heatingof the refractory packing.

The foregoing and additional objects of the present invention will beapparent from a consideration of the following description whichproceeds with reference to the accompanying drawings, wherein:

FIGURE 1 is an elevation view, showing in section the heat exchanger,including the packing and combustion chamber;

FIGURE 2 is a section view taken on line 22 of FIGURE 1;

FIGURE 3 is a top view of the structure shown in FIGURE 1, looking inthe direction of the arrows 33;

FIGURE 4 is a section view taken on line 4-4 of FIGURE 1; and

FIGURE 5 is a graph illustrating, in relative units, the temperaturerise of air versus the height of the tower.

Referring now to the drawings, a heat exchanger designated generally byreference numeral includes a tower 12 comprised of a shell 14 having aliner 1'6 of suitable heat resistant refractory composition. Within theshell is a packing designated gene-rally by reference numeral 18 andcomprised of a plurality of ceramic heat-resistant refractory bodiesreferred to as checkerwork and which are capable of being heated up andstoring heat and for thereafter imparting it to a blast of air which isintroduced through the heat exchanger. The refractory mass 1-8 issupported on a plurality of pedestals 20, or the like, which verticallysupport the mass of refractory checkers which are spaced to provide flowpaths for the gaseous combustion products which flow downwardly and theflow of air which passes through the stove in a manner to be described.The pedestals 20 not only support the refractory packing 18 but alsodefine a chamber 22 having an inlet 24 for the updraft of air which ispassed vertically upwardly through the mass of heated refractory toinitiate the flow of air for preheating and an outlet opening 26 for theexhaust products gene-rated in combustion chamber 28 during heat-up ofthe refractory packing 18.

The chamber 28 surmounts the tower 12 and is preferably offrusto-conical construction, being of brickwork or other suitable heatresistant refractory composition brick, or the like, 30.

Preferably the burner chamber 28 is frusto-conically constructed andthis is the configuration recommended for best results; however, othershapes, such as spherical,

are within the scope of the present invention but are not as eflicientor as useful as the frusto-conical shape. Within the chamber 28 there isburned a combination of fuel which is injected from a conduit 36, havingan outlet 34. The fuel being blast furnace gas, or the like, is at thetime of being injected, in the proper physical form for burning. Thecombustion-supporting gas for burning the fuel is in the form of air andsuch combustionsupporting gases are introduced through an inlet line 32having a control valve 75. The inlet 40 for the fuel is controlled by anarcuate gate 42 (FIGURE 4). Depending u-pon the position of the gate 42there will be introduced a precise, controllable rate and direction offlow of fuel indicated by the arrows 44 and 46. The inflow of fuel tendsto follow a swirling, vortexing movement and a sub-pressure zone iscreated at the central portion 48 of the inlet chamber 50. Suchdifferential pressure action tends to draw the air material into it andcreates flow paths indicated by reference numeral 52 (FIGURE 1) withinchamber 28. The burning action is highly controllable and unlike otherpreviously used for firing stoves will not scour or damage either thesidewalls of the upper chamber or the checkerwork. The cone shapedburner chamber is configured so that the gases are permitted to expandand completely burn but without such combustion occurring within thecheckerwork to cause its damage. The fuel and the air which describes adownwardly spiraling or vortexing path from chamber 50 into chamber 28,produces a turbulence between the two materials, thoroughly mixing themand causing the two to ignite. The ignition is within chamber 28 and theinterior walls 53 of the frusto-conically shaped chamber 30 promote suchcombustion and at a rapid and efficient rate. Flame which is propagatedby the combustion is controllable by the gate 42. For example, underhigh inflow rate and high volume inflow the vacuum which is produced isof a higher degree and the combustibles are drawn vertically higher andburning occurs at a higher level within chamber 28. Conversely, bydecreasing the flow rate and decreasing the volume, mixing andcombustion occurs at a lower level within chamber 28. By suitablyadjusting the position of the gate 42 and by regulating the amount ofinflow of combustibles from line 36 it is possible to effect completeand efficient combustion and moreover to regulate the flame propagationwithin chamber 28 so that none of the generated flame impinges upon theceramic packing within the tower and for this reason the refractory isnot damaged in spite of being exposed to a substantial temperature.

Since the entire cross section of the tower is filled with refractoryheat-absorbing media the tower is now more efiicient in imparting highertemperatures to a flow of air which is next passed upwardly through thetower from inlet 24 and following completion of the combustion withinchamber 28. It was previously the practice to use a portion of thevertical cross section as a combustion chamber and to that extent therewas unavailable the heat-absorbing refractory media which was capable ofheating the air or other upblast material intended for use in thesteel-making operations. Now such area is filled with checkerwork.

With the present invention it is possible to regulate the ratio of fuelto air both by means of controlling the valve 38 and by means ofcontrolling the rate of injection of air from line 32 and, knowing theburning rate and rate of generation of heat, it is possible to regulatethe position of the gate 42 to properly position the occurrence ofburning within chamber 28 and prevent flame propagation below the levelof the heat-absorbing media which, as previously described, is comprisedof a plurality of heat-absorbing ceramic or checkerwork 18.

During the burning cycle within combustion chamber 28 the pellets absorbthe heat and the products of combustion are dissipated verticallydownwardly leaving the system through port 26 and are vented toatmosphere through a stack, or the like (not shown). After sufficientheat has been absorbed by the media the burning operation is terminatedand this is followed by an air upblast and the air, as it passes throughthe heated refractory media which is formed as a packing within thetower, will become heated and elevated in temperature. Since the upperportion of the checkerwork performs the greatest heating function it ishighly advantageous that in the present invention this is the portionwhich is directly heated by combustion and is therefore at a highertemperature and is therefore best capable of imparting higher degrees ofheating temperature to the air as it progresses upwardly and becomessuccessively hotter. Since a greater quantity of heat is stored throughthe cross section of the stove by reason of its entire cross sectionbeing filled with ceramic particles, there is a greater capacity of thestove for heating the air and hence air in greater quantities can bepassed through the stove to meet the higher schedule of demand ofsteelmaking facilities. For example, referring to the graph of FIGURE 5,it will be seen that where efforts are made to increase the capacity ofa stove by merely increasing its height, the air will tend to reach amaximum temperature and this maximum temperature is not substantiallyimproved by increases in the height of the stove. On the other hand, byincreasing the cross section of the stove by removing the combustionchamber and filling it with ceramic media, as accomplished in thepresent invention, it is possible to make the upper portion of the stovemore eflicient for two reasons-onethere is a greater cross-sectionalarea of heat absorbing media and hence the volume of media at the upper20% of the stove is increased so that the capacity of the stove isincreased without increasing the height of the stove; and two, the upper20% of the stove is heated directly and to a proportionately greateramount which is proper since its contribution in the heating cycle isapproximately 80% of the entire heating function of the stove.

These results, as described, are achieved without in any Way detractingfrom the service life of the refractory media because the combustionwhile occurring at the point of maximum use in heat transfer iscontrolled in such a way that flame propagation will not occur into oragainst the checkerwork to consume the checkerwork.

The described burner system is capable of use with leaner fuels and oneswhich require thorough and intimate mixing of the air and fuel.

The invention is also useful in retrofitting existing stoves. It hasbeen found that the capacity of stoves can be materially increased, andwithout expensive alteration, by merely removing the existing combustionchamber from within the confines or envelope of the tower and fillingsuch voided space with checkerwork and then disposing the heatingchamber at the top of the tower within a frusto-conical combustionchamber or spherical combustion chamber, according to the preference ofthe builder. The conditions of combustion are then accurately controlledby regulating the inflow of combustible material or fuel, the inflow ofair according to rate and amount to properly complete the process ofcombustion and regulate the propagation of flame within precise bounds.

The present invention is useful, of course, not only in themetal-producing industry but in many other industries as well where itis desired to supply substantial flows of heated gases in large amountsand rates and where such heating can be accomplished in an economicaland safe manner.

The composition of the ceramic packing is not, it should be understood,essential to the present invention; any particular refractory packing,which is heat absorbent, stable and is capable of supporting itsvertical weight i satisfactory so long as such refractory packing willdevelop flow paths so that the products of combustion can flowdownwardly and the air inblast can move upwardly through the packing tobe heated thereby. It is also essential, of course, that such refractorymaterial has sufficient heat resistivity that it will not disintegrateunder exposure to high heat and will not fuse or become joined togetherto plug the flows upwardly and downwardly, respectively, within thetower.

Although the present invention has been illustrated and described inconnection with a single example embodiment, it will be understood thatthis is illustrative of the invention and is by no means restrictivethereof. It is reasonable to be expected that those skilled in this artcan make numerous revisions and adaptations of the invention, and it isintended that such revisions and adaptations will be included within thescope of the following claims as equivalents of the invention.

I claim:

1. An improved stove for heating air in metal-producing operations andthe like, comprising a shell: a quantity of heat-absorbing refractorybodies contained in said shelland adapted to receive and store heattherein, means for selectively circulating a flow of hot, inert gasesthrough said shell and which sweep over said refractory bodies to impartheat thereto, a conically shaped combustion chamber surmounting saidshell and forming an upper chamber of said stove, a burner including anadjustable fuel/air mixer having means adapted to propagate a flamewhich is generated from a flow of fuel and air circulated spirallywithin said combustion chamber to effect the flame which substantiallyfills but is unimpinging against the refractory bodies contained in saidshell, and means for circulating in a counterflow manner through saidshell and refractory bodies a flow of air which is heated by sweepingover the mass of said r fractory bodies.

2. An improved stove for heating air in metal-producing operations andthe like, comprising a shell: a quantity of heat-absorbing refractorybodies contained in said shell and adapted to receive and store heattherein, means for selectively circulating a flow of gases through saidshell and which sweep over said refractory bodies to impart heatthereto, a conically shaped combustion chamber surmounting said shelland having an adjustable fuel/ air mixer having means adapted topropagate a flame which is generated from a flow of said fuel and aircirculated spirally within said combustion chamber to effect a flamewhich substantially fills but is unimpinging against the refractorybodies contained in said shell, means for circulating upwardly throughsaid shell and refractory bodies a flow of air which is heated bysweeping over the mass of said refractory bodies and means providing anoutlet for the combustion gases which are circulated downwardly throughsaid stove in countercurrent relation with the air which is circulatedupwardly through the refractory bodies when the combustion operation hasterminated.

3. An improved stove for heating air in metal-producing operations andthe like, comprising a shell: a quantity of heat-absorbing refractorybodies contained in said shell and adapted to receive and store heattherein, means for selectively circulating a flow of gases through saidshell and which sweep over said refractory bodies to impart heatthereto, a conically shaped combustion chamber surmounting said shelland having a burner adapted to propagate a flame which is generated froma flow of said fuel and air circulated spirally within said combustionchamber to effect a flame which substantially fills but is unimpingingagainst the refractory bodies contained in said shell, means forcirculating upwardly through said shell and refractory bodies a flow ofair which is heated by sweeping over the mass of said refractory bodies,said burner including means for injecting fuel vertically downwardlywithin the center of said combustion chamber, and means for providing aflow of combustion-supporting air which is caused to flow circularlyaround the interior surface of the said conical chamber along a spiralpath therein, the flow rate and speed of said combustion-supporting airbeing adjusted to locate the flame which is generated within saidchamber.

4. A heating stove for providing a flow of air in heated condition formetal-producing operations, comprising in combination: support meansdefining a generally vertically extending heating chamber, a pluralityof heat absorbing elements froming a relatively loose mass of suchelements which provide flow paths therebetween, means defining an airinlet to provide a flow of air which is directed upwardly through themass of heated articles and is heated thereby, a generallyfrusto-conically shaped combustion chamber at the upper end of saidstove which provides a location of burning for generating heat forraising the temperature of said heat-absorbing elements, and a burnerdisposed in said chamber and having an inlet port which directscombustion-supporting gas tangentially relatively to the interiorsurface of said chamber and which spirally follows such interior chamberwall, fuel supply means adapted to inject fuel centrally in relation tosaid spiral inlet flow of combustion-supporting gas, and regulatingmeans for controlling the rate of input flow of fuel andcombustion-supporting gas to control the flame propagation and flamelength within said combustion chamber.

5. A heating stove for providing a flow of air in heated condition formetal-producing operations, comprising in combination: support meansdefining a generally vertically extending heating chamber, a pluralityof heat absorbing elements forming a relatively loose mass of suchelements which provide flow paths therebetween, means defining an airinlet to provide a flow of air which is directed upwardly through themass of heated articles and is heated thereby, a combustion chamberdisposed generally collinearly with the mass of heat-absorbing elementsand located at the upper end of the stove to provide a location ofburning which generates heat for raising the temperature of saidheat-absorbing elements, and a burner disposed in said chamber andhaving an inlet port which directs combustion-supporting gastangentially relatively to the interior surface of said chamber andwhich spirally follows such interior chamber wall, fuel supply meansadapted to inject fuel centrally in relation to said spiral inlet flowof combustion-supporting gas to control the flame propagation and flamelength within said combustion chamber, and regulating means forcontrolling the rate of input fiow.

6. An improved heating chamber for use in combination with a stoveadapted for heating air in metal-producing operations and the like,comprising means defining an internal combustion chamber adapted forsurmounting a vertical heating stove and defining the upper portion ofsaid stove, means for injecting fuel interiorly of said chamber incombustible form and extending substantially centrally of said chamber,means providing an inlet flow of combustion-supporting gases which arecaused to move tangentially of the interior surface of said chamber, andregulating means for determining the rate of inflow of suchcombustion-supporting gases to control the extent of flame propagationwithin said chamber.

7. An improved heating chamber for use in combination with a stoveadapted for heating air in metal-producing operations and the like,comprising means defining an internal combustion chamber adapted forsurmounting a vertical heating stove and defining the upper portion ofsaid stove, means for injecting fuel interiorly of said chamber incombustible form and extending substantially centrally of said chamber,means providing an inlet flow of combustion-supporting gases which arecaused to move tangentially of the interior surface of said chamber,regulating means for determining the rate of inflow of suchcombustion-supporting gases to control the extent of flame propagationwithin said chamber, and control means for regulating the inlet flow ofinjected fuel.

8. An improved heating chamber for use in combination with a stoveadapted for heating air in metal-producing operations and the like,comprising means defining an internal combustion chamber adapted forsurmounting a vertical heating furnace and defining the upper portion ofsaid furnace, means for injecting fuel interiorly of said chamber incombustible form and extending substantially centrally of said chamber,means providing an inlet flow of combustion-supporting gases which arecaused to move tangentially of the interior surface of said chamber, andregulating means for determining the rate of inflow of suchcombustion-supporting gases to control the extent of flame propagationwithin said chamber, said flame propagation being controlled to beconfined entirely within said chamber and unimpinging against the stovein proximity therewith.

References Cited UNITED STATES PATENTS 1,689,042 10/1928 McGee 263191,770,277 7/1930 McGee 263-19 1,942,762 1/1934 McGee 26319 3,082,9953/1963 Krapf 26319 FREDERICK L. MATTESON JR., Primary Examiner.

JOHN J. CAMBY, Examiner.

